As befits a man regarded as perhaps the most lyrical voice in contemporary popular music, the witness statement read to a Los Angeles court by Leonard Cohen was unusually poetic in its phrasing.

"I want to thank the court, in the person of your honour," Cohen told an LA county superior court judge, "for the cordial, even-handed and elegant manner in which these proceedings have unfolded. It was a privilege and an education to testify in this courtroom."

However dignified his prose and the proceedings, Cohen's testimony marked the end of a long and decidedly ugly episode in the 77-year-old singer's life, which has culminated in the jailing of his former manager for harassment.

Kelley Lynch, 55, was sentenced to 18 months in a Californian prison and five years probation for what the sentencing judge, Robert C Vanderet, called a "long, unrelenting barrage of harassing behaviour" towards Cohen, that the singer said had made him fear for his life.

Lynch, a jury had been told, had targeted Cohen with thousands of long, abusive voicemails and rambling emails that could run to 50 pages, denouncing him as a "sick man" and "common thief", and suggesting that he "needed to be taken down and shot".

"'Cohen is going to be hung,'" the singer drily told jurors at one point, "is not agreeable to hear."

The case was given added piquancy through the long and, recently, dramatic history between the Canadian singer and his harasser. Cohen sued Lynch in 2005, a year after he had dismissed her as his manager, claiming she had stolen $5m (£3.1m) from his personal accounts and investments and left him virtually penniless. The court found in his favour and ordered Lynch to pay him $9.5m, but her lawyers claimed she was unreachable, and she has never repaid the money or faced criminal charges.

The theft prompted the hard-up Cohen to begin touring again after five years in a Zen Buddhist monastery in California. Marathon tours of Europe, north America and Australasia met with ecstatic reviews and were enormously popular, going no small distance to repair the hole in his retirement fund. Billboard magazine reported that the 2009 world tour alone had earned Cohen $9.5m.

Cohen told the court that Lynch's campaign of harassment had begun shortly after he fired her in late 2004, having been tipped off that the glowing reports he had received about his financial investments were untrue, and subsequently discovering that most of his career earnings were gone.

Lynch had been a long-time family friend – both her parents had worked with Cohen, and she had managed him for 17 years – and Cohen acknowledged in court that they had had a "brief intimate relationship" during their time working together.

She had reacted to her dismissal, he said, by calling him repeatedly – "it started with just a few, but it eventually accelerated to 20 or 30 a day" – in tones that became more threatening, and ignoring restraining orders not to contact him. "It makes me feel very conscious about my surroundings," Cohen said. "Every time I see a car slow down, I get worried." Prosecutors showed the jury 10 binders of printed emails, which they said Cohen had received from Lynch since February 2011 alone.

In his opening statements, Michael Kelly, a public defender representing Lynch, said the case was "about relationships and how relationships oftentimes get messy". Lynch, he said, is "not a celebrity. She's not in the Rock and Roll Hall of Fame… so she's at a disadvantage here."

The messages, her defence argued, had been "cries for help" after the 2005 court finding had destroyed her reputation. But prosecutor Sandra Jo Streeter said that Lynch had embarked on the campaign of harassment as revenge. "This is nothing more than the unravelling of a con," she said.

The court case is the latest twist in the remarkable career of one of the most influential artists of his generation. Born in Montreal in 1934, Cohen first made his name as a poet before turning to music in the late 1960s. His lyrical gifts and highly distinctive downbeat baritone earned him a cult following among generations of music fans, along with an unshakeable reputation for morose melancholy.

Many feared his monastic retreat had signalled the end of his recording career; in fact, being "forced to go back on the road to repair the fortunes of my family and myself", he told the New York Times recently, was "a most fortunate happenstance because I was able to connect… with living musicians. And I think it warmed some part of my heart that had taken on a chill."

Cohen has spoken of late of an increasing preoccupation with mortality, but judging from his delicately waspish statement to the court, he has lost little of that fire. "I want to thank the defendant Ms Kelley Lynch for insisting on a jury trial, thus... allowing the court to observe her profoundly unwholesome, obscene and relentless strategies to escape the consequences of her wrongdoing," he said.

"It is my prayer that Ms Lynch will take refuge in the wisdom of her religion, that a spirit of understanding will convert her heart from hatred to remorse, from anger to kindness, from the deadly intoxication of revenge to the lowly practices of self-reform."